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    SubjectRe: RFC on io-stalls patch
    On Tue, Jul 15 2003, Andrea Arcangeli wrote:
    > On Tue, Jul 15, 2003 at 11:18:38AM +0200, Jens Axboe wrote:
    > > On Tue, Jul 15 2003, Jens Axboe wrote:
    > > > > BTW, the contest run times vary pretty wildy. My 3 compiles with
    > > > > io_load running on 2.4.21 were 603s, 443s and 515s. This doesn't make
    > > > > the average of the 3 numbers invalid, but we need a more stable metric.
    > > >
    > > > Mine are pretty consistent [1], I'd suspect that it isn't contest but your
    > > > drive tcq skewing things. But it would be nice to test with other things
    > > > as well, I just used contest because it was at hand.
    > >
    > > Oh and in the same spirit, I'll do the complete runs on an IDE drive as
    > > well. Sometimes IDE vs SCSI shows the funniest things.
    >
    > this is the first suspect IMHO too. Especially given the way that SCSI
    > releases the requests.

    2.4.21 + 2.4.22-pre5 + 2.4.22-pre5-axboe is running/pending on IDE now
    here.

    > One more thing: unlike my patch where I forced all drivers to support
    > elevator-lowlatency (either that or not compile at all), Chris made it
    > optional when he pushed it into mainline, so now the device driver has
    > to call blk_queue_throttle_sectors(q, 1) to enable it. Otherwise it'll
    > run like 2.4.21.

    Right, but both IDE and SCSI sets it. IDE is still the best to bench io
    scheduler performance on, though.

    --
    Jens Axboe

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